World-systems analysts have drawn our attention to the importance of the long-standing worldwide struggles of subaltern groups to defend their livelihoods and address fundamental conflicts of our times. Climate change, financial volatility, and rising inequality are exposing the existential threats the global capitalist system poses to growing numbers—many of whom once enjoyed some of its benefits. These urgent challenges create possibilities for social movements to attract more widespread support for alternatives to global capitalism. Using data on transnational social movement organizations (TSMOs) from 1953-2013, we assess possibilities for counter-hegemonic movements to provide the organizational infrastructure for a global movement to transform the world-system. We describe the organizational foundations for transnational cooperation among social movements and consider what changes in the population suggest about its counter-hegemonic potential. Our study reveals substantial organizational expansion, greater participation from actors in the periphery, regionalization, radicalization in the issue frames pursued by activist organizations, and network ties that suggest more limited and strategic engagement with the inter-state system. We attribute these changes to U.S. hegemonic decline, the end of the Cold War, and changes in inter-state institutions.